Handle case when sh:order is a list

[jsheunis]

This will cause ordering in a rendered form to break, so we need to use some default value (e.g. first element in list/array) or only accept decimal values for sh:order, meaning there should be some log or error if this is not the case. Also, LinkML's shaclgen.py might need to be patched to not turn order into a list under some circumstances.